This invention relates to a serial-access memory device having a plurality of memory cell arrays in which data can be stored and among which data can be transferred.
The prior art abounds in serial-access memory devices with single memory cell arrays, ranging from the video random-access memory (VRAM) and multiport dynamic random-access memory (multiport DRAM) used in the frame buffers of workstations and personal computers to the first-in-first-out (FIFO) devices used in the field memories of digital television, facsimile machines, copy machines, and assorted video equipment. VRAM and multiport DRAM permit both random access to an arbitrary address and serial access starting from an arbitrary address. FIFO memories simply store serial input data starting at address zero and output the same serial data again from address zero.
Applications of serial-access memories are expected to increase with the rising performance requirements of workstations and personal computers, and the emergence of high-definition television (HDTV) and other advanced television technology. In many of these applications, and particularly in applications that implement complex data-processing functions, serial-access memory devices must be interconnected so that data can be transferred from one storage location to another.
Mutual interconnections among existing serial-access memories, however, require intermediary buffers and other peripheral devices. A large number of control signals must be provided to control both the memory devices themselves and their peripheral devices. The design of the memory system becomes unduly complex.
In many cases the memory system must also operate at very high speed. At present this is especially true in computer and workstation applications, but the need for high-speed memory is becoming more general because of the development of HDTV and advanced electronic office equipment. It is not easy to make a large and complex set of control signals meet high-speed timing requirements. Design of a high-speed memory system therefore becomes exacting, difficult, and expensive.